Tenant does not have rights to any land per se so this shouldnt even be necessary but if the backyard was expressed in the lease and they are paying for that as an amenity then you need an amendment not addendum 

As mentioned, the owner came down to the amount of his loan pay-off on the first house very quickly- the contract amendment came back within the hour - and I need to communicate the second set of positive meth results from late last week, soon.

Amend the past 3 years (2012, 2013, 2014), this would disallow the change in accounting method, and claim the depreciation that should have been taken during those 3 years, and reduce the basis for the additional depreciation that was allowable3. 

Given his situation I'm thinking that if it's possible, amend the lease to cancel the special for him. 

This way, if you want to modify things later on, you can just make amendments to the specific addenda.

Read the rules and their subsequent amendments for yourself and you will find a way.Also, there are exceptions the rules.

Again, §1250 property does not have Ordinary Recapture so there is no Ordinary Gain to recognize.In year X, when you receive or change the agreed amount to be paid, you theoretically should go back to amend the original tax filing to adjust the gain ratio and recognize the proper gain in the first year and pay any interest and penalties, if due and recalculate the proper gain in the final year.

No amendments to it.

Contractor requests we amend to a 1099 Box 3.

I'm assuming I should correct and amend the original lease first and then do a simple renewal form?